Axle gear noise can be caused by insufficient lubricant, incorrect backlash, tooth contact, worn/damaged gears or
the carrier housing not having the proper offset and squareness.

Gear noise usually happens at a specific speed range. The noise can also occur during a specific type of driving
condition. These conditions are acceleration, deceleration, coast, or constant load.

When road testing, first warm-up the axle fluid by driving the vehicle at least 5 miles and then accelerate the vehicle
to the speed range where the noise is the greatest. Shift out-of-gear and coast through the peak-noise range. If the
noise stops or changes greatly:

•

Check for insufficient lubricant.

•

Incorrect ring gear backlash.

•

Gear damage.

Differential side gears and pinions can be checked by turning the vehicle. They usually do not cause noise during
straight-ahead driving when the gears are unloaded. The side gears are loaded during vehicle turns. A worn pinion
mate shaft can also cause a snapping or a knocking noise.

BEARING NOISE

The axle shaft, differential and pinion bearings can all produce noise when worn or damaged. Bearing noise can be
either a whining, or a growling sound.

Pinion bearings have a constant-pitch noise. This noise changes only with vehicle speed. Pinion bearing noise will
be higher pitched because it rotates at a faster rate. Drive the vehicle and load the differential. If bearing noise
occurs, the rear pinion bearing is the source of the noise. If the bearing noise is heard during a coast, the front
pinion bearing is the source.

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Differential bearings usually produce a low pitch noise. Differential bearing noise is similar to pinion bearing noise.
The pitch of differential bearing noise is also constant and varies only with vehicle speed.

Axle shaft bearings produce noise and vibration when worn or damaged. The noise generally changes when the
bearings are loaded. Road test the vehicle. Turn the vehicle sharply to the left and to the right. This will load the
bearings and change the noise level. Where axle bearing damage is slight, the noise is usually not noticeable at
speeds above 30 mph.

LOW SPEED KNOCK

Low speed knock is generally caused by a worn U-joint or by worn side-gear thrust washers. A worn pinion shaft
bore will also cause low speed knock.

VIBRATION

Vibration at the rear of the vehicle is usually caused by:

•

Damaged drive shaft.

•

Missing drive shaft balance weight(s).

•

Worn or out of balance wheels.

•

Loose wheel lug nuts.

•

Worn U-joints or C/V joints.

•

Loose/broken springs.

•

Damaged axle shaft bearing(s).

•

Loose pinion gear nut.

•

Excessive pinion yoke run out.

•

Bent axle shaft(s).

Check for loose or damaged front end components or engine/transmission mounts. These components can contrib-
ute to what appears to be a rear end vibration. Do not overlook engine accessories, brackets and drive belts.

DRIVELINE SNAP

A snap or clunk noise when the vehicle is shifted into gear (or the clutch engaged) can be caused by:

•

High engine idle speed.

•

Transmission shift operation.

•

Loose engine/transmission/transfer case mounts.

•

Worn U-joints or C/V joints.

•

Loose spring mounts.

•

Loose pinion gear nut and yoke.

•

Excessive ring gear backlash.

•

Excessive side gear to case clearance.

The source of a snap or a clunk noise can be determined with the assistance of a helper. Raise the vehicle on a
hoist with the wheels free to rotate. Instruct the helper to shift the transmission into gear. Listen for the noise, a
mechanics stethoscope is helpful in isolating the source of a noise.

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FRONT AXLE - C205F

DIAGNOSTIC CHART

Condition

Possible Causes

Correction

Wheel Noise

1. Wheel loose.

1. Tighten loose nuts.

2. Faulty, brinelled wheel bearing.

2. Replace bearing.

Axle Shaft Noise

1. Misaligned axle tube.

1. Inspect axle tube alignment. Correct
as necessary.

2. Bent or sprung axle shaft.

2. Inspect and correct as necessary.

3. End-play in pinion bearings.

3. Refer to pinion pre-load information
and correct as necessary.

4. Excessive gear backlash between
the ring gear and pinion.

4. Check adjustment of the ring gear and
pinion backlash. Correct as necessary.

5. Improper adjustment of pinion gear
bearings.

5. Adjust the pinion bearings pre-load.

6. Loose pinion yoke nut.

6. Tighten the pinion yoke nut.

7. Scuffed gear tooth contact
surfaces.

7. Inspect and replace as necessary.

Axle Shaft Broke

1. Misaligned axle tube.

1. Replace the broken shaft after
correcting tube mis-alignment.

2 Vehicle overloaded.

2. Replace broken shaft and avoid
excessive weight on vehicle.

3. Erratic clutch operation.

3. Replace broken shaft and avoid or
correct erratic clutch operation.

4. Grabbing clutch.

4. Replace broken shaft and inspect and
repair clutch as necessary.

Differential Cracked

1. Improper adjustment of the
differential bearings.

1. Replace case and inspect gears and
bearings for further damage. Set
differential bearing pre-load properly.

2. Excessive ring gear backlash.

2. Replace case and inspect gears and
bearings for further damage. Set ring
gear backlash properly.

3. Vehicle overloaded.

3. Replace case and inspect gears and
bearings for further damage. Avoid
excessive vehicle weight.

4. Erratic clutch operation.

4. Replace case and inspect gears and
bearings for further damage. Avoid erratic
use of clutch.

Differential Gears Scored

1. Insufficient lubrication.

1. Replace scored gears. Fill differential
with the correct fluid type and quantity.

2. Improper grade of lubricant.

2. Replace scored gears. Fill differential
with the correct fluid type and quantity.

3. Excessive spinning of one
wheel/tire.

3. Replace scored gears. Inspect all
gears, pinion bores, and shaft for
damage. Service as necessary.

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Condition

Possible Causes

Correction

Loss Of Lubricant

1. Lubricant level too high.

1. Drain lubricant to the correct level.

2. Worn axle shaft seals.

2. Replace seals.

3. Cracked differential housing.

3. Repair as necessary.

4. Worn pinion seal.

4. Replace seal.

5. Worn/scored yoke.

5. Replace yoke and seal.

6. Axle cover not properly sealed.

6. Remove, clean, and re-seal cover.

Axle Overheating

1. Lubricant level low.

1. Fill differential to correct level.

2. Improper grade of lubricant.

2. Fill differential with the correct fluid
type and quantity.

3. Bearing pre-loads too high.

3. Re-adjust bearing pre-loads.

4. Insufficient ring gear backlash.

4. Re-adjust ring gear backlash.

Gear Teeth Broke

1. Overloading.

1. Replace gears. Examine other gears
and bearings for possible damage.

2. Erratic clutch operation.

2. Replace gears and examine the
remaining parts for damage. Avoid erratic
clutch operation.

3. Ice-spotted pavement.

3. Replace gears and examine remaining
parts for damage.

4. Improper adjustments.

4. Replace gears and examine remaining
parts for damage. Ensure ring gear
backlash is correct.

Axle Noise

1. Insufficient lubricant.

1. Fill differential with the correct fluid
type and quantity.

2. Improper ring gear and pinion
adjustment.

2. Check ring gear and pinion contact
pattern.

3. Unmatched ring gear and pinion.

3. Replace gears with a matched ring
gear and pinion.

4. Worn teeth on ring gear and/or
pinion.

4. Replace ring gear and pinion.

5. Loose pinion bearings.

5. Adjust pinion bearing pre-load.

6. Loose differential bearings.

6. Adjust differential bearing pre-load.

7. Mis-aligned or sprung ring gear.

7. Measure ring gear run-out. Replace
components as necessary.

8. Loose differential bearing cap bolts.

8. Inspect differential components and
replace as necessary. Ensure that the
bearing caps are torqued tot he proper
specification.

9. Housing not machined properly.

9. Replace housing.

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